My buddy's Dad was in great health at 88 living in England, he told me a while back. He was walking extensively up and down hills near Carlyle. Then one day he slipped and broke a hip, I think, was hospitalized. My friend said he went over to see him and he was in bad shape weeks later. They more or less fixed the hip issue, but in the mean time he had degraded to where he could barely walk. He never got back into it, being bedridden for a few weeks did him in.
My greatgrandmother lived to 102. My Dad told me she was plowing behind a mule at 90, which might be exaggerated. But a kind of random event can suddenly put you out of shape and getting back to it can be problematic, you just don't recover.
My Dad's side of the family were long "livers", several centenarians and nearly all lived past 90 including my parents, so I figure I should plan on that for me (if I don't drink myself to liver failure). My wife keeps saying I'll easily outlive her, that is a prospect I do not relish, at all. I have a dream about it occasionally and wake up in a sweat.
My Dad's mother was in good health when her husband died (at 87), and she went six months later. My Dad said she just gave up living.